Working overtime increases your risk of coronary heart disease (CHD), according to a report published May 12 in the European Heart Journal.

Using data from a study called Whitehall II, which followed 6,014 British civil servants for an average of 11 years between 1991 and 2004, researchers examined the risk of CHD in people who did not work overtime compared to their workaholic office-mates. Those who worked three hours or more extra per day had a 56 percent higher risk of heart-related problems, including angina (chest pain resulting from a temporary lack of blood to the heart) and heart attacks.

"Our findings suggest a link between working long hours and increased CHD risk, but more research is needed before we can be confident that overtime work would cause CHD," said lead author Marianna Virtanen, from the Finnish Institute of Occupational Health, in a prepared statement. The link was independent of several better-known risky behaviors such as smoking, being overweight, having high cholesterol or having a type A personality.

"One plausible explanation for the increased risk could be that adverse lifestyle or risk factor changes are more common among those who work excessive hours compared with those working normal hours," said Virtanen. It's also possible that the chronic stress associated with working long hours adversely affects metabolic processes, she said.

Roughly half of the study subjects didn't work overtime. But 21 percent worked one extra hour, 15 percent worked two extra hours, and 10 percent worked three hours or more extra per day.

"At the moment there is no research on whether reduction in overtime work reduces CHD risk. Further research on this topic is therefore needed," said senior author Mika Kivimäki, from University College London, in a prepared statement. Kivimäki plans to investigate whether working long hours predicts changes in lifestyle, mental health and traditional risk factors, such as blood pressure, blood glucose and cholesterol.

It's unclear whether the findings generalize to blue-collar workers and employees in the private sector, the authors report.

In the journal, the study was accompanied by an editorial written by Gordon McInnes from University of Glasgow Western Infirmary. "If the effect is truly causal, the importance is much greater than commonly recognized," McInnes wrote. "Physicians should be aware of the risks of overtime and take seriously symptoms such as chest pain, monitor and treat recognized cardiovascular risk factors, particularly blood pressure, and advise an appropriate lifestyle modification."

McInnes concluded by quoting the English philosopher Bertrand Russell: "If I were a medical man, I should prescribe a holiday to any patient who considers work important."

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